A pressure resistance property and an on-state resistance are important indicators of performance of a rectifier element such as a diode. As a rectifier element that can achieve a high pressure resistance and a low on-state resistance, attention is being given to a Schottky barrier diode (SBD) that uses a III-nitride compound semiconductor having a wide band gap. An example of the related art document on SBD includes Patent Document 1 (JP 2006-156457 A).
In the cross sectional view of FIG. 19, schematically shown is an example of the structure of the SBD. As shown in FIG. 19, an SBD 100 has the stacking structure in which a buffer layer 120, an n+-type GaN layer 122, and an n-type GaN layer 123 are epitaxially grown on a sapphire substrate 101 in this order. On the upper part of the stacking structure, formed is an anode electrode 112 that forms a Schottky junction with the top surface of the n-type GaN layer 123. On another end of the stacking structure that is lower than the upper end portion, formed is a cathode electrode 113 that is in ohmic contact with the n+-type GaN layer 122.